What is the purpose of fixing in film processing?

The purpose of fixing in film processing is fundamentally to dissolve unexposed silver halides. During the development process, exposed silver halides react with the developer chemicals to form a visible image, while unexposed areas remain unchanged. The fixing stage is crucial because it removes this unreacted silver halide from the film, ensuring that the developed image is permanent and no longer sensitive to light. Without proper fixing, the unexposed halides could later react to light, leading to unwanted fogging or changes to the image over time.

While enhancing image contrast, establishing base density, and preventing further exposure are important aspects of film processing, they occur through different stages and processes. Fixing primarily serves the essential function of ensuring that the developed image is stable and retains its intended appearance, eliminating any remnants of unexposed materials.